Light emitting diode package with diffuser and method of manufacturing the same

ABSTRACT

The invention relates to an LED package for facilitating color mixing using a diffuser and a manufacturing method of the same. The LED package includes a substrate with an electrode formed thereon, and an LED chip mounted on the substrate. The LED package also includes an encapsulant applied around the light emitting diode chip, containing a diffuser. The LED package further includes a lens part disposed on the light emitting diode chip and the encapsulant to radiate light in a wide angle. The LED package allows light from the light emitting diode chip to be emitted out of the package without distortion. The invention allows light to exit through the encapsulant containing the diffuser and the lens part, achieving uniform diffusion and emission of light from the LED chip, thereby increasing a radiating angle and obtaining a uniform light source.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/491,947, filed Jul. 25, 2006, now U.S. Pat. No. 7,501,656, whichclaims priority to Application No. KR 10-2005-0067859, filed on Jul. 26,2005, the entire contents of each of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a Light Emitting Diode (LED) packageincorporating a diffuser to facilitate color mixing and to amanufacturing method of the same. More particularly, the inventionrelates to an LED package in which a diffuser is applied to anencapsulant disposed in an upper part of an LED chip to achieve colormixing, enabling uniform emission without distortion of light from theLED chip in a wide radiating angle, thereby facilitating color mixingwhile reducing a thickness and enhancing a degree of freedom of a lenspart, and to a manufacturing method of the same.

2. Description of the Related Art

In general, various sizes of LED packages are used for backlight unitsof mobile phones or Personal Digital Assistants (PDAs).

Such conventional LED packages are increasingly reduced in its thicknessas the backlight units are becoming slimmer.

For such backlight units, the LED packages are popular as light sourcestherefor, and thus various structures or shapes of LED package arecurrently examined and developed.

The LED packages used for LCD Televisions or monitors are structurallycategorized into an edge lighting type, a top emitter, and a sideemitter. The most important factor among these LED packages is toachieve good color mixing to make a white light source.

Such an example of a conventional LED package is illustrated in FIG. 1.

The conventional LED package 200, disclosed in U.S. Patent No.2005-0057144, includes a substrate 205 with electrode patterns 207 a and207 b formed thereon, and an LED chip 210 mounted on the electrodepattern 207 b and electrically connected to the electrode patterns 207 aand 207 b by wires 211.

The conventional LED package 200 has a reflecting frame 212 disposed onthe substrate 205 for housing the LED chip 210, and a reflecting layer214 formed on an inner side of the reflecting frame 212. The reflectinglayer 214 serving as a reflecting surface is made of Al and/or Ag havinghigh reflectivity deposited or painted thereon.

In addition, a wavelength-converting material part 220 is formed in aninner space of the reflecting frame 212 where the LED chip 210 ismounted. The wavelength-converting material part 220 comprisestransparent resin containing a phosphor 222 a and a diffuser 222 b, andencapsulates the LED chip 210.

In the above-described LED package 200, when emission takes place fromthe LED chip 210 and light is emitted, the light is directed to thewavelength-converting material part 220 by the reflecting layer 214. Thelight then collides with the phosphor 222 a contained in thewavelength-converting part 220 to excite the phosphor 222 a, and isscattered by a plurality of diffusers 222 b contained in thewavelength-converting material part 220. As a result, light having alonger wavelength than the light that was incident onto the phosphor 222a exits the package due to the interaction between the phosphor 222 aand the diffuser 222 b.

Although the conventional technology is useful for elongating thewavelength of light emitted from the LED chip 210 and emitting whitelight, it does not necessarily allow uniform light emission. Theconventional technology allows color mixing to generate white light, butemits white light only forward without a variety in radiating angles.Further, as it realizes white light using the phosphor 222 a, it hasmediocre color reproducibility.

Another conventional LED package 250 is illustrated in FIG. 2.

As disclosed in Japanese Patent Application Publication No. 2001-60724,the LED package 250 includes an LED chip 260 positioned in a lamphousing 255 having a hollow part, electrodes 262 a and 262 b drawn outfrom the LED chip 260, and an encapsulant 270 filled in the lamp housing255 for fixing the LED chip 260 and the electrodes 262 a and 262 b.

In such a conventional LED package 250, the lamp housing 255 having ahollow part is disposed such that its emitting surface is positioned ina lower part. Then, the encapsulant 270 composed of transparentthermosetting resin with glass beads 272 having a high refractive ratiomixed therein at a suitable ratio is injected into the hollow part ofthe lamp housing 255 from the back of the LED chip 260.

Then, after the glass beads 272 precipitate in the encapsulant 270 madeof transparent thermosetting resin, the encapsulant 270 is heated andcured to complete the LED package 250.

In such a conventional LED package 250, the glass beads 272 in theencapsulant 270 of transparent thermosetting resin function as adiffuser and scatter light to some degree. However, the light isdirected only forward in a not-so-wide radiating angle due to the hollowpart of the lamp housing 255, and it is difficult to reduce thethickness of the LED package 250 due to the structural characteristicsof the electrodes 262 a and 262 b and the lamp housing 255.

In addition, the conventional LED package 250 is complicated tomanufacture, thus not suitable for mass production.

FIG. 3 illustrates yet another conventional LED package 300. Theconventional LED package 300 includes a base substrate 305 withelectrodes 310 a and 310 b formed thereon, an LED chip 312 mounted onand connected to the electrodes 310 a and 310 b, and a molded frame 315having a groove, thus being fixed around the LED chip 312.

Then, a molding member 317 containing a diffuser 317 a is filled in thegroove of the molded frame 315. This conventional LED package 300achieves high luminance and contrast ratio using the diffuser 317 acontained in the molding member 317 made of transparent resin, therebyenabling a high contrast display in a large angle of visibility in highprecision.

However, the conventional LED package 300 also emits light only forwardfrom the molded frame 315, and does not achieve excellent lightemission.

When applied to the backlight units to produce white light using red,green, and blue lights, each of the above described LED packages 200,250 and 300 is required in a plural number to uniformly illuminate alarge area and mix colors, increasing the number of components.

Therefore, the conventional LED packages 200, 250 and 300 result inincreased manufacturing costs of the LCD products due to the increasednumber of components.

SUMMARY OF THE INVENTION

The present invention has been made to solve the foregoing problems ofthe prior art and therefore an object of certain embodiments of thepresent invention is to provide an LED package using a diffuser whichachieves uniform emission of light generated from an LED chip to make auniform light source, and a manufacturing method of the same.

Another object of certain embodiments of the invention is to provide anLED package using a diffuser which emits light generated from an LEDchip in a wide radiating angle without distortion of light, therebyincreasing a degree of freedom and reducing a thickness of a lens part,and a manufacturing method of the same.

Further another object of certain embodiments of the invention is toprovide an LED package using a diffuser which constitutes a LiquidCrystal Display (LCD) backlight unit in a fewer number, therebydecreasing the number of LED package components and reducing themanufacturing costs of the LCD backlight unit, and a manufacturingmethod of the same.

According to an aspect of the invention for realizing the object, thereis provided a light emitting diode package including: a substrate withan electrode formed thereon; a light emitting diode chip mounted on thesubstrate; an encapsulant applied around the light emitting diode chip,the encapsulant containing a diffuser; and a lens part disposed on thelight emitting diode chip and the encapsulant to radiate light in a wideangle, whereby light from the light emitting diode chip is emitted outof the package without distortion.

Preferably, the substrate has a step formed on an upper surface thereof,the step surrounding a portion of the substrate where the light emittingdiode chip is mounted.

Preferably, the substrate has a reflective layer formed on a sidesurface of a recessed portion formed on an upper surface thereof, thereflective layer surrounding the light emitting diode chip mounted onthe substrate.

Preferably, the lens part is made of a material mixed with a phosphor.

Preferably, the lens part is made of a material mixed with a diffuser.

Preferably, the lens part is made of a material mixed with a phosphorand a diffuser.

According to another aspect of the invention for realizing the object,there is provided a manufacturing method of a light emitting diodepackage including steps of: providing a substrate with an electrodeformed thereon; mounting a light emitting diode chip on the substrate;applying an encapsulant containing a diffuser to cover the lightemitting diode chip; and attaching a lens part on the encapsulant,whereby light from the light emitting diode chip is emitted out of thepackage without distortion.

In addition, the diffuser comprises an opal based material.

Further, the opal based material is one selected from a group consistingof barium titanate, titanium dioxide, aluminum oxide, silicon dioxideand combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a sectional view illustrating a conventional LED package;

FIG. 2 is a sectional view illustrating another conventional LEDpackage;

FIG. 3 is a sectional view illustrating yet another conventional LEDpackage;

FIG. 4 is a sectional view illustrating an LED package using a diffuseraccording to the present invention;

FIG. 5 is an exploded view illustrating the LED package according to thepresent invention;

FIG. 6 is an exploded view illustrating a cavity of the LED packageusing a diffuser according to the present invention;

FIG. 7 is a perspective view illustrating the LED package using adiffuser with an encapsulant applied on the substrate of the LED packageusing a diffuser according to the present invention;

FIG. 8 is a view illustrating traces of light scattered, reflected anddiffused out of the LED package using a diffuser according to thepresent invention; and

FIGS. 9( a) and (b) are views illustrating the LED packages using adiffuser of the invention disposed in an array to be used for an LCDbacklight.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Preferred embodiments of the present invention will now be described indetail with reference to the accompanying drawings.

As shown in FIG. 4, an LED package 1 using a diffuser according to thepresent invention has a substrate 10 with electrodes 5 a and 5 b formedthereon. The substrate 10 preferably has a planar structure molded withmolding material, and has each of the electrodes 5 a and 5 b formedthereon to provide power to an LED chip 20 described later.

The LED chip 20 is mounted on an upper part of the substrate 10 andelectrically connected to the electrodes 5 a and 5 b by wire bonding,etc. The invention is applicable to either a horizontal type of LED chip20 with all electric terminals formed on an upper surface thereof, or avertical type of LED chip 20 with electric terminals formed on bothupper and lower surfaces thereof.

In addition, a step 25 is formed on an upper surface of the substrate 10to surround the portion where the LED chip 20 is mounted.

Such a step 25 is formed in an annular form on an upper surface of thesubstrate 10, and as described later, an encapsulant 30 is applied in anappropriate amount in a recessed portion formed by the step 25 and thusprevented from spreading over the substrate 10.

In addition, the encapsulant 30 is applied to cover the LED chip 20 andthe substrate 10. As shown in detail in FIG. 7, the encapsulant 30,which is applied on the substrate 10 to surround the LED chip 20,contains a diffuser 32 therein. The encapsulant 30 serves to maintain auniform light source generated from the LED chip 20, and has a diffuser32 added thereto in order to enable diffusion of light.

Therefore, the encapsulant 30 adjusts the degree of scattering,transmittance and refraction of light with the diffuser 32 containedtherein, thereby assisting uniform emission of light.

The encapsulant 30 is made of resin such as silicone or epoxy, and thediffuser 32 is made of an opal based material, i.e., one selected from agroup consisting of, barium titanate, titanium dioxide, aluminum oxide,silicon dioxide and combinations thereof. The diffuser 32 is added tothe encapsulant 30 in the amount of 25 weight % or less of the totalweight of the encapsulant 30.

In addition, the LED package 1 has a lens part 40 disposed above the LEDchip 20 and the encapsulant 30 to emit light in a wide radiating angle.The lens part 40 is formed by curing epoxy resin and the like, andpreferably is made of transparent epoxy. Preferably, the lens part 40may be made of a material with a phosphor 42 mixed therein.

Moreover, preferably, the lens part 40 may be made of a material with adiffuser 32 mixed therein instead of a phosphor 42, or both a phosphor42 and a diffuser 32 mixed therein.

As shown in FIG. 6, the LED package 1 of the invention may preferablycomprise a so-called cavity structure in which the LED chip 20 ismounted in a recessed portion on the substrate 10, and thus surroundedby a reflecting layer 50 formed on a side surface of the recessedportion.

The reflecting layer 50 may be formed by plating or depositing metalselected from a group consisting of Al, Au, Ag, Ni, W, Ti and Pt, or byapplying a paint of high reflectivity.

A manufacturing method of the LED package 1 using a diffuser accordingto the present invention will now be explained in detail.

The manufacturing method of the LED package using a diffuser starts witha step of providing the substrate 10 with the electrodes 5 a and 5 bformed thereon.

The electrodes 5 a and 5 b are formed on the substrate 10 to supplypower to the LED chip 20, and as described later, the step 25 is formedon an upper surface of the substrate 10, surrounding the portion wherethe LED chip 20 is mounted.

In addition, as shown in FIG. 5, the substrate 10 may comprise astructure, in which the LED chip 20 is positioned on a protrudingportion of the substrate 10, or as shown in FIG. 6, may comprise acavity structure, in which the LED chip 20 is disposed within a recessedportion surrounded by the reflecting layer 50.

Next, the LED chip 20 is disposed on the substrate 10. The LED chip 20is mounted on the substrate 10, and electrically connected to theelectrodes 5 a and 5 b of the substrate 10 by wire bonding.

Then, the encapsulant 30 is applied on the LED chip 20 and the substrate10.

In this step, the encapsulant 30 is transparent epoxy resin containing adiffuser 32. As shown in FIG. 7, the amount of the encapsulant 30applied is determined beforehand such that the encapsulant 30 is filledinside the recessed portion formed by the step 25 of the substrate 10and does not spread over the substrate 10 to drip due to surface tensionof the encapsulant 30.

Next, the lens part 40 is attached on the encapsulant 30. In this step,the lens part 40 is placed over the encapsulant 30, and as shown in FIG.8, the encapsulant 30 fills up a recess 44 formed on a bottom surface ofthe lens part 40 to attach the lens part 40 on the substrate 10. Then,the encapsulant 30 is cured to integrally form the lens part 40 with thesubstrate 10.

In this step, the lens part 40 may be made of transparent material,which however may be prepared in advance to contain either a phosphor 42or a diffuser 32 mixed therein, or both a phosphor 42 and a diffuser 32mixed therein.

As shown in FIG. 9, the LED package 1 using a diffuser according to thepresent invention may be arranged in a plural number in a row to bedisposed as an array in an LCD backlight unit.

In the LED package 1 using a diffuser with above describedconfiguration, the lens part 40 is attached to the substrate 10 via theencapsulant 30 containing the diffuser 32, which is applied on thesubstrate 10 where the LED chip 20 is mounted.

In the LED package 1 using a diffuser according to the presentinvention, when light is generated from the LED chip 20, the light isemitted through the encapsulant 30 and the lens part 40, and thusemitted in a wide radiating angle. Specifically, light is diffused morebroadly due to the diffuser 32 contained in the encapsulant 30 and/orthe lens part 40, achieving a wider radiating angle, thereby uniformlyilluminating a large area with a fewer number of LED packages 1.

When the light is emitted from the LED chip 20 to pass through theencapsulant 30 and the lens part 40, the light is diffused at thediffuser 32, thereby reflected or scattered in more various directions,allowing uniform mixing of colors. This is suitable for a structure suchas the LCD backlight unit, which requires uniform mixing of red, greenand blue lights.

In addition, the LED package 1 is a structure in which the light fromthe LED chip 20 is emitted out of the package without distortion by theassistance of only the diffuser 32. Thus, the lens part 40 is free to beconfigured in various structures. That is, the lens part 40 can havevarious structures such as in a small height or asymmetrical shapedepending on the structural characteristics of the LCD backlight unit,thereby increasing a degree of freedom of the lens part 40.

In addition, the lens part 40 can be made of a material mixed with aphosphor 42 in addition to the diffuser 32, enabling more various colormixing, thereby attaining desired good quality white light.

According to the present invention set forth above, the light generatedfrom the LED chip passes through the encapsulant containing the diffuserand the lens part to exit the package, achieving uniform diffusion andemission without distortion of light, thereby obtaining a uniform lightsource with an enlarged radiating angle.

In addition, as light generated from the LED chip is emitted in a widerangle by the diffuser, the lens part can be configured variously such aswith a lower height, thereby reducing the thickness and increasing adegree of freedom of the lens part.

Furthermore, the invention allows a wide radiating angle, enablingconstruction of the LCD backlight unit with a fewer number of LEDpackages and with a reduced number of LED package components, therebyreducing the manufacturing costs of the LCD backlight unit.

While the present invention has been shown and described in connectionwith the preferred embodiments, the invention may be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein. It will be apparent to those skilled inthe art that modifications and variations can be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

1. A manufacturing method of a light emitting diode package comprisingsteps of: providing a substrate with an electrode formed thereon;mounting a light emitting diode chip on the substrate; applying anencapsulant containing a diffuser to cover the light emitting diodechip; and attaching a lens part on the encapsulant, whereby light fromthe light emitting diode chip is emitted out of the package withoutdistortion.
 2. The light emitting diode package according to claim 1,wherein the diffusers comprises an opal based material.
 3. Themanufacturing method of a light emitting diode package according toclaim 2, wherein the opal based material is one selected from a groupconsisting of barium titanate, titanium dioxide, aluminum oxide, andsilicon dioxide and combinations thereof.